Chapter 26 Sweet Corn

Fresh Market Sweet Corn IPM Scouting Procedures

Processing Sweet Corn IPM Scouting Procedures

Download the IPM ECB, CEW, FAW Scouting Form (188K pdf).

Link to IPM Elements for Fresh-market and Processing sweet corn.

Link to New York Sweet Corn Crop Profile

Link to Resource Guide for Organic Insect and Disease Management

26.1 Recommended Varieties

Processing
Plant varieties recommended by processors.

Fresh-market
Listed in approximate order of maturity within each class.

Sweet corn varieties are categorized by their genotype. The most common varieties are normal or sugary (su), sugar enhanced (se), and supersweet or shrunken types (sh2). Other varieties include sweet breeds, synergistic or sweet genes, and improved supersweets. Su types have a short shelf life with sugars rapidly converted to starch soon after picking. Se varieties have a higher initial sugar content which can potentially extend storage life three to five days. Se varieties are either homozygous or heterozygous. Homozygous se corn has two doses of genes and will be sweeter than heterozygous se corn with a single dose of genes. Sh2 varieties are genetically distinct from the su and se varieties. The sugar content of supersweets is twice that of standard sweet corn, and the storage life is extended five to ten days. Not only are supersweets much sweeter, but the texture is distinct from the other two types. Supersweet varieties are also more difficult to establish than se and su types. They germinate poorly at temperatures below 60°F and are easily damaged by rough handling.

Warning. Sh2 varieties need to be isolated by at least 250 feet or 12 days in silking from su and se types or cross pollination will result in a starchy, inedible kernel. Su and se varieties can be planted side by side without this occurring. Be aware that even among corn of the same genotype, pollen from a bicolor or yellow variety on the silk of a white variety will result in an ear with bicolor characteristics. Two to five border rows will protect against this type of cross pollination.

26.2 Planting Methods

Plastic mulches. Clear, perforated, plastic mulch will speed the maturity of early plantings. Seed two weeks earlier than usual in double rows spaced 14 to 16 inches apart on five to six foot centers. Apply herbicide and cover with clear plastic mulch (1 to 1-1/14 mil) four feet wide. Keep plastic over plants for approximately 30 days or until daytime temperatures consistently exceed 75°F. At that time, cut plastic and remove it from the field, usually when plants are six to 12 inches tall.

Another approach is to apply a spun fiber (floating) row cover after planting. Although soil temperatures are not increased as quickly as with plastic, there are advantages. These include use of standard row spacing, less danger of plant injury due to high temperatures, ease of application, and the ability to reuse row covers for several seasons.

26.3 Fertility

Use lime to maintain a pH of 6.0 to 6.2. If soil magnesium is below 100 pounds per acre, use high magnesium lime to adjust pH. For long-term benefit, if soil test zinc is between 1/2 and one pound per acre, broadcast 1/2 pound zinc per acre. If soil zinc is below 1/2 pound per acre, apply one pound zinc per acre. When zinc levels are marginal, an application of one pound of zinc in the fertilizer band may be helpful.

Growers may use the Pre-sidedress Soil Nitrogen Test (PSNT) to determine the need for sidedress nitrogen. The PSNT determines the nitrogen available from manures, cover crops, and previous crops. Contact your County Extension Agent for more details.

Cornell cover crop decision tool

Cornell article: "Closing the phosphorus cycle on vegetable farms: releasing soil-bound phosphorus to support springtime seedling growth."

Go to Cornell Nutrient Analysis Lab website to find out how to get soil samples tested.

Cornell Soil Health website and manual

SARE Publication: "Building Soils for Better Crops"

SARE publication: "Managing Cover Crops Profitably"

Table 26.3.1 Recommended nutrients based on soil tests.
N pounds/acre	P2O5 pounds/acre				K2O pounds/acre			Comments
	Soil Phosphorus Level				Soil Potassium Level
	low	med.	high		low	med.	high
120-140	120	80	40		120	80	40	Total recommended.
40	80	40	0		80	40	0	Broadcast and disk-in.
40	40	40	40		40	40	40	Band place with planter.
40-60	0	0	0		0	0	0	Sidedress when corn is 6" to 12" high.1
1: A second sidedressing could replace the preplant, broadcast application of nitrogen if applied before corn is 12" tall. This is preferable on leachable soils.

26.4 Harvesting

Under normal temperatures, most varieties reach maturity 18 to 21 days after silking. Supersweets have a wider "harvest window" than su and se varieties. Maximum quality is attained when corn is picked at peak maturity and rapidly cooled by hydrocooling or vacuum cooling followed by top or body icing if corn is to be shipped. Corn should be stored at 32° to 40°F and 98 percent relative humidity.

See Cornell GAPsNET

See UC Davis post harvest guide for sweet corn

See Cornell "Smart Marketing" series

See USDA grade standards for fresh sweet corn and processed sweet corn

See USDA Agricultural Marketing Service site

See current wholesale prices from US markets

SARE Publication: "Marketing Strategies for Farmers and Ranchers"

SARE Publication: "Direct Marketing Resource Guide"

26.5 Disease Management

| Anthracnose | Maize dwarf mosaic virus | Barley yellow dwarf |Cereal yellow dwarf | Northern corn leaf blight |
| Common rust | Seed rots | Common smut | Stewart's wilt |

SARE Publication: "A Whole-Farm Approach to Managing Pests"

Cornell corn disease checklist

Time for concern: All season
Key characteristics: Small spots appear on the leaves. These spots may enlarge and become tan in the center with red, reddish brown, or yellowish orange borders. See Reference 1.

See photo gallery of sweet corn viruses

Cornell corn disease checklist

Time for concern: After June 15
Key characteristics: The MDMV system consists of a mosaic pattern of lighter and darker green streaks along the veinal and interveinal tissues. See Reference 2.

Cornell corn disease checklist

Time for concern: Planting to harvest
Key characteristics: The most prominent symptom associated with BYDV/CYDV- infected plants are purpling or yellowing along the leaf margins, running the length or both lower and upper leaves. The color involved depends upon the corn variety infected.

Cornell corn disease checklist

Ohio State NCLB fact sheet

Time for concern: Whorl through tassel
Key characteristics: Long, elliptical, grayish green or tan lesions ranging from 1 inch to 5 inches in length develop on the lower leaves first, and then progress to younger tissue. Lesions often look "boat shaped."

See photo gallery of common rust

Cornell corn disease checklist

Organic management of common rust in sweet corn

Time for concern: Whorl through tassel
Key characteristics: Rust appears in the field as oval to elongated cinnamon-brown pustules scattered over the surface of the leaves. See Reference 5.

Cornell corn disease checklist

Organic management of seed rots in sweet corn

Time for concern: Seed
Key characteristics: Seed rots cause pre- and postemergence damping-off and poor stand establishment. See Reference 1.

See photo gallery of common smut

Cornell corn disease checklist

Organic management of common smut in sweet corn

Time of concern: Seedling through ear formation
Key characteristics: Commonly found on the ears, tassels, and nodes, smut is a gall composed of a white, smooth covering containing black, greasy, or powdery spores. See Reference 5.

See photo gallery of Stewart's wilt

Cornell corn disease checklist

Organic management of Stewart's wilt in sweet corn

Time of concern: From emergence through harvest
Key characteristics: Yellow to brown stripes or streaks with wavy or irregular margins on leaves signal Stewart’s wilt. The Stewart’s wilt bacteria overwinter in corn flea beetles. For management options, see Corn flea beetle.

2000 Cornell Report: Stewart's Wilt Incidence in New York Sweet Corn in 2000: Upstate (text)

26.6 Insect Management

| Corn flea beetle | Japanese Beetle | Seedcorn maggot | Cutworms | Corn leaf aphid |
| Sap beetle | Western corn rootworm | European corn borer |
| Corn earworm | Fall armyworm | Slugs |

SARE Publication: "Manage Insects on Your Farm: A Guide to Ecological Strategies"

SARE Publication: "A Whole-Farm Approach to Managing Pests"

26.6.1 Corn flea beetle, Chaetocnema pulicaria, vectors the bacterium, Erwinia stewartii, which is the pathogen that causes Stewart’s wilt.

See pictures of CFB damage
See pictures of CFB life cycle

See photo gallery of Stewart's wilt

Organic management of Corn flea beetle in sweet corn

Time of concern: Seedling through mid-whorl
Key characteristics: Black or brassy in color, the corn flea beetle is about 1/16 inch in length and often jumps when disturbed. Beetles chew narrow channels in corn leaves. For a description of Stewart’s wilt, see Section 26.5 Disease Management. See Reference 7. and http://www.nysaes.cornell.edu/ent/factsheets/

Florida fact sheet with pictures of JB on many crops

Time of concern: During ear formation when adults move from other crops into corn.
Key characteristics: The adult stage is the damaging stage on corn. The adults are metallic green or greenish brown beetles about 1/3 to 5/8 inches in length, with reddish wing covers. They feed on a wide reange of agricultural and landscape plants and are a major pest of turf. In areas where it is abundnt, it can cause severe damage to corn by feeding on the husks, foliage, kernals, and silk.

*Restricted use only. ** Not for use in Nassau/Suffolk counties.
Check NYS PIMS (Product, Ingredient, and Manufacturer System) to see if the label is current for New York. SPECIAL NEW YORK RESTRICTIONS MAY APPLY. (http://magritte.psur.cornell.edu/pims/)

See pictures of SCM damage
See pictures of SCM life cycle

Organic management of SCM in sweet corn

Time of concern: Seed sprouting through emergence
Key characteristics: Adult flies are slender, 3/8 inch long, and grayish black in color. Maggots are yellowish white. Infested seeds and other plant parts are hollowed out. Damaged plants are weak and may not develop. Stand may be poor. See Reference 8. and http://www.nysaes.cornell.edu/ent/factsheets/

Ontario, Canada cutworm fact sheet

Time of concern: Seedling stage
Key characteristics: Mature larvae, 1 1/4 to 1 3/4 inches in length, may appear "greasy." Larvae curl into a C when disturbed. Young plants with small holes in the leaves, wilted leaf tips, or lodged plants are indicative of cutworms. See Reference 10 and http://www.nysaes.cornell.edu/ent/factsheets/pests.html

See pictures of CLA damage
See pictures of CLA life cycle

Organic management of CLA in sweet corn

Time of concern: Early tassel through harvest
Key characteristics: Corn leaf aphids are greenish blue with black legs. Colonies buildup in the curls of leaves and on stems on the upper part of the plant. Infestations produce large amounts of honeydew on which black, sooty mold develops. High populations can cause discoloration of outside husk layers. Corn leaf aphids are an important vector of maize dwarf mosaic virus. See Reference 2. and http://www.nysaes.cornell.edu/ent/factsheets/

Florida sap beetle fact sheet

Time of concern: Ear fill through harvest
Key characteristics: Beetles of the predominate species are black, about 3/8 inch long, and have two, reddish orange spots on each wing. They are frequently found in leaf axils and ear tips and often infest ears previously damaged by worms or birds. The larvae, which are small, white, and maggot-like may also be found at the ear tip. See http://www.nysaes.cornell.edu/ent/factsheets/

See pictures of WCRW damage
See pictures of WCRW life cycle

Organic management of WCRW in sweet corn

Time of concern: Mid-May - Mid-July, larvae; July-September, adults.
Key characteristics: The adult beetles are yellow and brown with yellow stripes on their wings. Adults feed on leaves, tassels, and silks; larvae feed on roots. The larvae are 1/4 inch long when full grown and white with a brown head and "tail." See http://www.nysaes.cornell.edu/ent/factsheets/

See pictures of ECB damage
See pictures of ECB life cycle
See Cornell ECB fact sheet

Ontario, Canada fact sheet on ECB

Organic management of ECB in sweet corn

Time of concern: Mid-May through September
Key characteristics: Eggs are laid in scale-like masses on the undersides of leaves. The larvae are white to gray. The head capsule is dark brown. Larvae are 3/4 inch long when fully developed. The adult is a yellowish to reddish brown moth, about one inch in length. In whorl stage, corn damage may appear in leaves as a series of small pin holes perpendicular to the leaf midrib. Second brood adults are much less likely to oviposit on whorl stage corn than are first brood adults. Ear feeding can make ears unmarketable. Damage to stems is evidenced by the presence of sawdust-like material in leaf axils and broken tassels and stems. See References 11 and 12. or http://www.nysaes.cornell.edu/ent/factsheets/

See pictures of CEW damage
See pictures of CEW life cycle
See Cornell CEW fact sheet

Organic management of CEW in sweet corn

Time of concern: Mid-July through September
Key characteristics: The yellowish, round eggs, laid mostly on silks, are deposited singly. The adult moth has a wingspan greater than one inch and varies in color from yellowish tan to brown. Forewings have two dark spots. The larvae vary in color, with green, brown, or pink stripes. Skin is rough with characteristic short microspines. Full-grown larvae are about 3/4 inch in length. See References 10 and 14. or http://www.nysaes.cornell.edu/ent/factsheets/

The most recent trap catches of the WNY Sweet Corn Pheromone Trap Network are posted and updated each Tuesday during the growing season.

See pictures of FAW damage
See pictures of FAW life cycle
See Cornell FAW fact sheet

Organic management of FAW in sweet corn

Time of concern: Mid-July through September
Key characteristics: Spherical eggs are laid in masses of 100 or more at random locations throughout the plant. Egg masses are covered with body hairs, giving them a gray to green appearance. The adult moth has a 1 1/2 inch wingspan. When full grown, larvae are tan, green, or very dark and reach a length of 1 1/2 inches. The front of the head has an inverted, white Y. Because eggs are laid in masses, larval infestations are concentrated and corn in the vicinity will have a shot-gunned appearance. See Reference 15. or http://www.nysaes.cornell.edu/ent/factsheets/

26.7 Weed Management

Key characteristics: Weed fact sheets provide a good reference for common weed identification. See Reference 16. Also, see Virginia Tech Weed Identification Guide.

Cornell Weed Ecology and Management Laboratory website

Ontario, Canada weed identification gallery

Penn State Weed Fact Sheets

SARE Publication: "A Whole-Farm Approach to Managing Pests"

Management Option	Recommendation
Scouting/thresholds	Weeds may be unevenly distributed over a field. Localized areas of severe weed infestations or atypical conditions, such as poorly drained areas, high spots, and field edges, may be recorded on a weed map. A weed map should be on file for each field. Make a rough sketch of the field, including landmarks, boundaries, crop row direction, compass directions, roads, planting date, map preparation date, and any other important details. The following information should be indicated on the map: species of weed, size of weed, density of each species, and distribution of weed. Weed maps should be updated for each field twice per year: soon after planting to evaluate the success of the current season's program and at or near harvest to help predict weed control practices that will be necessary for the following year. Processing Sweet Corn IPM Scouting Procedures Fresh Market Sweet Corn IPM Scouting Procedures Cornell Weed Assessment List (scouting form) Manitoba, Canada weed scouting guide
Site selection	Refer to weed maps to avoid problem weeds when choosing fields for sweet corn.
Cultivation	Cultivation is useful in sweet corn weed control. See Cornell fact sheet on mechanical weed control. SARE Publication: "Steel in the Field"
Banding herbicides	Banding of herbicides at planting is useful in sweet corn production when combined with culitvation. Herbicide banding can result in up to 60 percent savings in herbicide costs. Contact CCE for more information.
Cover Crops, Weed Seed Bank Assessment	See report on using buckwheat as a weed control cover crop See report on estimating weed seed banks SARE publication: "Managing Cover Crops Profitably" Cornell cover crop decision tool Cornell buckwheat cover crop handbook Cornell Forage Species Selection Tool

Compound(s)
Comparing Environmental Risks of Pesticides In the "Field Use EIQ" column is the range of EIQ (Environmental Impact Quotient) values for the rate range recommended for each pesticide (lower EIQ = lower environmental impact). Other pesticide risk models are useful for specific purposes. WIN-PST is required for some USDA NRCS conservation plans.
Common name Trade name	Rate/ Product	PHI (days)	REI (hours)	Field  Use EIQ	Comments
preplant incorporated
butylate + safener (yellow nutsedge)
Sutan + 6.7-E 6.7 lb/gal	4.75-7.33 pt		12	35-54	Apply and incorporate 3-4 inches. Better results if applications are made in late-planted corn when the soil is warm and tubers are sprouting. Sutan + is best in wet seasons, Eradicane in dry.
EPTC + safener (yellow nutsedge)
Eradicane 6.7-E 6.7 lb/gal	4.75-7.33 pt		12	37-57
preplant incorporated or preemergence
alachlor (annual grasses)
** *MicroTech 4 lb/gal	2.0-3.5 qt		12	30-53	NOT FOR USE IN NASSAU/SUFFOLK COUNTIES. Use alone or in combination with atrazine. Rates vary with soil type and timing of application.
preplant incorporated, preemergence, postemergence
atrazine (annual grasses)
*AAtrex Nine-0	0.8-1.38 lb		12	11-28	For use preemergence and postemergence.  Rates of 1 lb AI/A usually will not result in carryover, residual problems in New York.  If carry over is a concern lower rates should be applied postemergence.  Corn is tolerant at all stages but weeds are most sensitive soon after emergence.  Use of an oil adjuvant will increase weed control.  Do not apply to corn taller than 12 inches.  At pH < 5.5 atrazine is tightly bound to soil colloids.  Liming soils to pH values greater than 7 may result in bound atrazine being released, injuring sensitive crops.
*AAtrex 4L 4 lb/gal	1.5-2.5 pt		12	12-25
dimethenamid-p  (grasses, yellow nutsedge, galinsoga, and nightshade)
(†)Outlook 6.0     6 lb/gal	see comments		12	9-14	NOT FOR USE IN NASSAU AND SUFFOLK COUNTIES.   Apply 12 to 14 fluid oz on coarse textured soils with less than 3% OM to 18 to 21 fluid oz on medium or fine textured soils with 3% or greater OM.  Post application timing is when corn is <12” tall.
metolachlor (annual grasses; selected broadleaves; nutsedge)
** *Dual II Magnum 7.64 lb/gal	1-1.67pt	60	24	18-31	NOT FOR USE IN NASSAU /SUFFOLK COUNTIES. Surface applications work well provided raiinfall occurs within 3 to 5 days. In dry periods, incorporation is desirable. Rates should be chosen with attention to organic matter levels. Early maturing varieties may show short-term injury, particularly in cold, wet seasons.
** *Dual Magnum 7.62 lb/gal	coarse soils 1.0-1.33 pt medium soils 1.33-1.67 pt fine soils 1.67-2 pt		R24	18-26 26-31 31-37	NOT FOR USE IN NASSAU AND SUFFOLK COUNTIES.Postemergence-Dual Magnum may be applied postemergence with atrazine but without oil. Apply before grass and broadleaf weeds have more than 2 true leaves and before corn exceeds 5" in height. This tank mix may be applied to corn up to 12" in height, but after 5" it must be applied as a directed spray, not broadcast over the top of the corn.
preemergence or postemergence
mesotrione
Callisto 4 lb/gal	Pre 6-7.7 fl oz Post 3-7.7 fl oz		12	3-4 2	Callisto controls largely broadleaf weeds and has soil residual as well as post emergence activity on sensitive species. Due to potential for increased injury, Callisto may not be applied with nitrogrn-based fertilizers. Crop oil concentrates and non-ionic surfactants may be used.
pendimethalin (velvetleaf and triazine resistant common lambsquarters)
Prowl 3.3EC 3.3 lb/gal	1.8-4.8 qt		24	20-53	Corn should be planted at least 1.5 inch deep to ensure good soil coverage. May be applied pre or post. Apply when corn has 2 or less leaves and velvetleaf is <1 inch. Under wet conditions, may cause poor brace root development leading to lodging. Twelve month crop rotation restriction (+ deep plowing) for beets and spinach.
Prowl H2O 3.8 lb/gal	2-4 p t		24	23-46
postemergence
2,4-D (perennial broadleaves)
multiple products 3.8 lb/gal					Label varies with manufacturer and formulation. Apply before corn is 6" tall. Repeat after harvest. Plow or disk 1-2 weeks after fall spray.
atrazine
See recommendations under “PREPLANT INCORPORATED, PREEMERGENCE, POSTEMERGENCE”
bentazon + 1% crop oil v/v (yellow nutsedge)
Basagran 4 lb/gal	1.5-2 pt		12	13-18	Apply when nutsedge is 6-8" tall. Effective in hot, humid weather. Nutsedge must be thoroughly wetted. Two applications may be necessary.
clopyralid (ragweed, hairy galinsoga, smartweed, wild buckwheat, dandelion, hairy nightshade, Canada thistle)
**Stinger 3EC 3 lb/gal	0.33-0.66 pt	30	12	2-5	NOT FOR USE IN NASSAU AND SUFFOLK COUNTIES. Make up to 2 broadcast applications, not to exceed 2/3pt/A per year. The recommended retreatment interval is 21 days. Do not apply to sweet corn that is greater than 18 in tall. Stinger may be tank mixed with other herbicides labeled for sweet corn.
carfentrazone (selected broadleaves)
Aim 1.9EW 1.9 lb/gal	0.5 fl oz		12	<1	Apply postemergence up to the 8th collar growth stage but when weeds are actively growing and not taller than 4 in or rosettes greater than 3 in. in diameter. Use of a nonionic surfactant is essential. Under dry conditions a crop oil concentrqte may ncrease performance but will also increase crop response. Overlapping during field applications will result in increased crop injury. Weeds controlled include common lambsquarters, eastern black nightshade, redroot pigweed, and particularly velvetleaf.
foramsulfuron (annual and perennial grasses and broadleaves)
Option 35WDG	1.5-1.75oz	45	12		Option may be applied broadcast when corn is in the V1-V6  (visible collars) growth stage and may be applied twice in a season.  From V6 to V8 Option must be applied with drop nozzles and may not be applied after the V8 stage as ears may be malformed.  Maximum use per season may not exceed 3.5oz.  Methylated seed oil plus a spray grade nitrogen fertilizer are recommended spray adjuvants.  Non-ionic surfactants, crop oil concentrates and vegetable seed oils are not recommended.  Varietal sensitivity is variable.  Check with seed companies, processors, and Extension Educators regarding current information about varietal tolerances.
nicosulfuron (annual grass and quackgrass)
Accent  0.75 lb/lb	0.66 oz		4	<1	Control of crabgrass is limited while broadleaf control is limited to redroot pigweed. Accent is now registered for use on both processing and fresh market sweet corn, however the manufacturer will not assume liability for crop injury due to differential varietal sensitivity. Contact your local DuPont representative for information regarding the potential sensitivity of specific varieties.  Requires use of either a crop oil concentrate (1% v/v) or NIS (.25% v/v). The addition of an ammonium nitrogen fertilizer or ammonium sulfate is also recommended.  Cautions:  Accent may be applied broadcast to corn up to but not taller than 12"". If taller than 12"", Accent MUST be applied as a directed spray that will not put the herbicide in the whorl of the plant as ear/tassel malformation may result.  Accent may not be tank-mixed with any product not actually found on the product label or special local need label.
halosulfuron (yellow nutsedge, pigweed, ragweed and velvetleaf)
Permit 75DF 0.75 lb/lb	0.67 oz	12		<1	Permit may be applied a maximum of two times with rates not to exceed 0.67 oz at either application. A nonionic surfactant (NIS) or crop oil concentrate (COC) is required. Research at CU has shown that crop response is greater with COC. Review product label for information on use of fertilizer solutions and varietal responses.
topramezone
Impact 2.8lb/gal	0.75 fl oz	45	12		For postemergence control of several broadleaf weeds including triazine-resistant lambsquarters, ragweed, nightshades, and velvetleaf as well as several annual grasses. The label recommends tank-mixing Impact with atrazine and adjuvants, particularly MSO and a nitrogen fertilizer source.
preemergence or postharvest
glyphosate (quackgrass, perennial broadleaves)
Roundup Weather Max or OLF 5.5  lb/gal	1 - 1.4 pt (weeds< 6") 1.4 - 2 pt (weeds> 6")		4	8-11   11-15	Before crop emergence or after fall harvest, spray on actively growing quackgrass when 4 to 5 leave are present, or when weed is 8" in height. Apply during sunny weather. Wait three days between application and plowing and disking. For broadleaves, apply in fall when weeds are actively growing.
*Restricted use only. Check NYS PIMS (Product, Ingredient, and Manufacturer System) to see if the label is current for New York. SPECIAL NEW YORK RESTRICTIONS MAY APPLY. (http://magritte.psur.cornell.edu/pims/)